Many gas turbine engines combustors are formed having sheet metal walls. It is common to manufacture these sheet metals walls by seam welding several sheet metal components together, including to form the exit ducts of such combustors. However, seam welds undergo thermal stresses during engine operation as warmer parts of the sheet metal walls thermally expand, while colder parts of the sheet metal walls do not thermally expand, or expand less. This thermal imbalance is accentuated by the necessity of having an overlap at the seam weld between the two sheet metal walls. This overlap prevents cooling air from outside of the combustor from reaching the vicinity of the seam weld.